Private industry and the U.S. government have a greatly increasing need for a safe, reliable, and economical way to transport and deploy satellites and other payloads into selected orbits around the Earth. Satellites for communication, weather monitoring, Global Positioning navigation, Earth sensing, microgravity research, and the like are being carried into space by conventional rockets at extremely high costs. The conventional rockets that can be used to carry and deploy satellites are multiple stage rockets having one or more expendable stages that are sequentially discarded during ascent and dumped into the ocean. The last stage of such a rocket remains in orbit where it contributes to a growing mass of useless space junk orbiting around the Earth.
One of the most significant problems facing industry with respect to satellite deployment is the extremely high cost to transport the satellite from the Earth into a desired orbit. As an example, one launch of an unmanned Delta rocket presently costs approximately $40 million, and a single launch of a larger unmanned Titan rocket presently costs approximately $200 million. Each rocket is used only once, so a failure during any part of the mission can be very costly, and typically the costs are substantially unrecoverable. These high costs are prohibitive for many companies, and the result is an over-demand for use of satellites presently orbiting Earth.
The NASA space shuttle was developed in an attempt to reduce the cost of space travel and to minimize the amount of space junk resulting from a satellite deployment. The space shuttle uses a very complex winged stage, known as an orbiter, that carries three or more astronauts and a payload into orbit, and the orbiter is then flown back to Earth and landed at a landing strip. The orbiter is launched from Earth into space using two solid propellant booster rockets and a very large expendable liquid hydrogen fuel tank. The liquid hydrogen fuel is extremely volatile, and extensive redundant safety systems are required for each space shuttle launch, which increase the cost of each launch.
As the space shuttle climbs along its ascending trajectory, the liquid hydrogen is consumed and the large tank is jettisoned into the ocean and is never reused. The solid propellant booster rockets are also jettisoned and fall back to Earth into the ocean. The booster rockets are recovered from the ocean and reused only after extensive and expensive refurbishing. The orbiter returns to Earth through the outer atmosphere, and the astronauts guide the orbiter through the lower atmosphere using control surfaces on the orbiter's wings to fly the orbiter to the selected landing strip. Once the orbiter has landed, it can be reused with a new liquid hydrogen fuel tank and new or refurbished solid propellant booster rockets.
The space shuttle program has not achieved the goal of making space more accessible to private industry, due primarily to the loss of expensive hardware, the high cost of rocket booster refurbishment, and the cost of redundant safety systems required for a manned flight utilizing liquid hydrogen fuel.
For several years, aerospace companies and the U.S. government have been attempting to develop hypersonic flight technology and a single-stage-to-orbit (SSTO) vehicle as a better means of space transportation. The SSTO vehicle currently under consideration is designed to operate like a large, powerful airplane, wherein the vehicle takes off from Earth, accelerates to space, deploys its payload in a selected orbit, reenters Earth's atmosphere, and lands like an airplane at a landing strip. After refueling, it would be ready for a subsequent trip. However, such an SSTO vehicle has not yet been developed because of the enormous development costs and the size required of such a vehicle to accomplish the flight from Earth to an orbit and back. While efforts in the area for an SSTO vehicle have been pursued for well over ten years, such a vehicle has not yet been developed.